1. Field of the Invention
The described embodiments relate to a display device having touch sensors embedded in a pixel array and a data driving circuit thereof.
2. Discussion of the Related Art
A User Interface (UI) enables a person (i.e., a user) to easily control various electrical and electronic devices as he or she wants through communication between the user and the devices. Representative examples of the UI may include a keypad, a keyboard, a mouse, an On Screen Display (OSD), and a remote controller having an infrared communication or Radio Frequency (RF) communication function. UI technology continues to develop toward higher user sensibility and manipulation convenience. In recent years, the UI evolved into a touch UI, a voice recognition UI, and a 3D UI.
The touch UI is essentially adopted in portable information devices, such as smart phones and expanded to laptop computers, computer monitors, and home appliances. There has recently been proposed a technology in which touch sensors are embedded in the pixel array of a display panel (hereinafter called an “in-cell touch sensor”). In the in-cell touch sensor technology, touch sensors can be installed in a display panel without an increase in the thickness of the display panel. Such touch sensors are connected to pixels through parasitic capacitance. In a driving method, in order to reduce mutual influences attributable to the coupling of the pixels and the touch sensors, a 1 frame period may be subject to time division into a period in which the pixels are driven (hereinafter called a “display driving period”) and a period in which the touch sensors are driven (hereinafter called a “touch sensor driving period”).
In the in-cell touch sensor technology, an electrode connected to the pixels of the display panel is used as the electrode of the touch sensors. For example, the in-cell touch sensor technology may include a method of segmenting a common electrode for supplying a common voltage Vcom to the pixels of an LCD and using segmented common electrode patterns as the electrodes of the touch sensors.
Parasitic capacitance connected to the in-cell touch sensors is increased due to coupling between the in-cell touch sensors and the pixels. If parasitic capacitance is increased, touch sensitivity and touch recognition accuracy are deteriorated.
If an AC voltage having the same phase as a touch driving signal is supplied to the data lines of the display panel during the touch sensor driving period, parasitic capacitance of the touch sensor can be reduced because the amount of charges of the parasitic capacitance is reduced. In such a method, the data voltage of an input video is supplied to the data lines during the display driving period, and the AC voltage is supplied to the data lines during the touch sensor driving period. To this end, there is proposed a method of adding switch elements for switching the data voltage and the AC voltage in each output channel of a data drive Integrated Circuit (IC). However, such a method increases the chip size of the data drive IC and causes an increase in the IC cost.